Small portable computers such as “palmtops” can be conveniently carried in a pocket. Recent advances in shrinking the size of electronic components will soon allow these devices to perform all the functions of today's desktop computers. Additionally, a whole new category of “information appliances” has begun. These include portable wireless telephone/computers which can be used to access the Internet to send and receive e-mail and to interact on the World Wide Web. Also, personal digital assistant (PDA's) are becoming more and more popular.
Powerful and versatile as these devices are becoming, their use is greatly limited by non-existent or inadequate keyboards. Palmtops which rely on handwriting recognition have proven to be awkward, slow and error prone. Miniature keyboards commensurate with the size of small appliances are likewise frustrating, especially if the user needs to write something consisting of a few sentences or more. Voice recognition suffers from frequent errors and creates a lack of privacy when other people are near the speaker whose voice is being recognized. Further, voice recognition may not be used in all circumstances (e.g. the process of taking notes of a lecturer's lecture in an otherwise quiet auditorium may not be possible with voice recognition input systems but it is usually possible with a keyboard).
Keyboards for desktop and high quality laptop computers allow the user to comfortably, privately, quietly, and quickly “touch-type.” They have a number of desirable features in common. Most keyboards have a standard “QWERTY” layout which requires no learning on the part of the user (once the user has become familiar with this layout). The keys, which usually number 84 for a laptop computer, have full-sized tops whose center-to-center spacing is about 0.75 inches for both the horizontal and vertical axes. The length of the keyboard (the distance from the left edge of the left-most key to the right edge of the right-most key) is about 11 inches. Any reduction in this spacing has proven to slow down and frustrate the touch-typist. Additionally, the keys of these keyboards have sufficient “travel,” the distance the key moves when it is pressed, and tactile feedback, an over-center buckling action, that signals the user that the key has been pressed sufficiently.
Efforts have been made to provide keyboards that contain these features, yet collapse to a reduced size. Some designs only slightly reduce the size of “notebook” computers when folded. These are much larger than palmtop computers. IBM's ThinkPad 701C′ notebook computer folds in a single operation to reduce the keyboard case length (measured from the edges of its case) from 11.5 inches to 9.7 inches. Also see U.S. Pat. No. 5,543,787 which describes a foldable keyboard. U.S. Pat. No. 5,519,569 describes a keyboard which folds in multiple steps from a length of 10-11 inches to 6.125 inches. U.S. Pat. No. 5,654,872 describes a keyboard with keys that collapse when the lid is dosed to allow a thinner notebook computer.
Other designs of keyboards include those where the keyboard is hinged at the center of its length and folds about a vertical axis. U.S. Pat. No. 5,457,453 describes a keyboard that folds to greater than half its length. U.S. Pat. No. 5,574,481 describes a keyboard that folds in half and appears to have a non-standard layout of keys (the keys on the center fold axis have edges which lie in a straight line). U.S. Pat. No. 5,653,543 describes a keyboard that folds in half. U.S. Pat. No. 5,502,460 describes a keyboard with two vertical hinges that folds to greater than half its unfolded length.
U.S. Pat. Nos. 5,044,798 and 5,141,343 describe keyboards whose keys have user-selectable variable spacing. These designs have non-standard layouts (e.g., the “Enter” key is rotated ninety degrees) and no self-containing housing.
Reducing the size of a keyboard by folding it is a challenging task because of the physical limitations of the materials that make up the parts of the keyboard assembly. For example, the keys usually include a plastic keytop having a thickness and a spring or support member below the keytop that has a height. The key is typically mounted to a base or a platform that includes a panel such as a printed circuit board or a membrane, which also has a thickness. A housing is usually provided to carry the key and its base and panel. The housing also has a thickness. The folded keyboard can be considerably thick when all the thicknesses and heights are added together and multiplied by the number of sections which are folded or stacked on one another. Advances have been made in the materials used for the parts of the keyboard to provide thinner plastic wall sections, for example. However, consumers desire portable devices that are sturdy and large enough to be easily used, yet can be conveniently carried or stored without taking up a large amount of space.
Keyboards electrically communicate information to information appliances. Most keyboards have printed circuit boards or membranes located underneath their keys. When a key is pressed it shorts the circuits in a particular column or row. The matrix of columns and rows that make up a keyboard is continually scanned by a controller to determine which keys have been pressed. Such an arrangement is described, for example, in U.S. Pat. No. 5,070,330. The electronic configuration of most keyboards thus necessitates a matrix of conductors that limits the collapsing of the keyboard to a certain size.